The 0.72 OD gear is perfect for a 3.90 rear. A 28" diameter tire with a 3.90 rear and 0.72 OD will give you 2190 RPMs at 65 MPH. A 235/70R15 tire has a 28" diameter and recommended rim width is 6 to 8 inches. I'm not sure how wide your stock rims are.

Part of your decision will depend on what you think looks good on the truck. Other options are available and will still maintain a 28" diameter. If you decide to use a slightly larger diameter tire than 28" then your RPMs will be a little less but not a problem. A 29" tire will have your engine doing 2115 RPMs at 65 MPH.

1965 Chevy C10 Shortbed 1/2-Ton Stepside
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